In this excerpt from his new book The Ravenous Brain, neuroscientist Daniel Bor explores how a brain injury reveals the truth about human consciousness.

On the night of Thursday, May 8, 1997, my father had a stroke. When I visited him in the hospital, I felt profoundly disturbed by what I witnessed. This sluggish, exhausted man in front of me looked like my father, but I knew, deep down, that he wasn't.

There were disconcerting clues that betrayed this impostor: He had effectively reverted from a sharp, responsible man into a confused child. Even more bizarrely, his attitude toward me would radically alter depending on whether I sat on the right or left side of his bed. When I sat on his right, he would take an interest in me, and we'd have a semi-coherent conversation. When I went instead to his left, it was as though I wasn't in the room. He simply wasn't aware of my presence.

From the first painful glimpse of my father's fractured consciousness, I understood how vital and fundamental this field is, and soon after I began to carry out research into how the brain generates our experiences.

There is nothing more important to us than our own awareness. We see the breathtaking beauty of snowcapped mountains, the exhilarating grace and speed of a cheetah on a hunt. We fall in love, or experience the joy of our child's first smile. All these, and everything else we care about, are conscious events. If none of these events were conscious, if we weren't conscious to experience any of them, we'd hardly consider ourselves alive-at least not in any way that matters.

When I'm reveling in a glowing pleasure, or even if I'm enduring a sharp sadness, I always sense that behind everything there is the privilege and passion of experience. Our consciousness is the essence of who we perceive ourselves to be. It is the citadel for our senses, the melting pot of thoughts, the welcoming home for every emotion that pricks or placates us. For us, consciousness simply is the currency of life.

But what actually is it? In The Ravenous Brain, I argue that consciousness is that choice mental space dedicated to innovation, a key component of which is the discovery of deep patterns within the contents of our awareness. This allows us to take great strides in every intellectual field we explore, as we weave a vast tapestry of meaning inside us. One consequence of this patient, piecemeal endeavor is that when we spot a chair, we don't see it according to its basic sensory features. Instead, we unavoidably recognize it as a chair, and immediately have access to a pyramid of meaning relating to this one object-what forms chairs take, what functions they serve, and so on. In fact, as we gaze around our world, we ineluctably view each component of the scene via the dense filter of the structure of knowledge we've acquired throughout our lives. Every single object on which we cast our eyes triggers a conscious wave of understanding, its own pyramid of meaning.

Consciousness concerns itself only with the most meaningful mental constructions and is ever hungry to build new patterns over existing architectures. To help in this aim, it itches to combine and compare any objects in our awareness. How the brain supports consciousness closely mirrors these functions. Those specialist regions of the cortex that manage the processing endpoints of our senses-for instance, areas involved in recognizing faces, rather than merely the colors and textures that constitute a face-furnish our awareness with its specific content. But there is also a network of our most advanced general-purpose regions that directly draws in all manner of content from these specialist regions. This is the core network, incredibly densely connected together, both internally and across major regions throughout the brain. In this inner core, multiple sources of meaningful, potentially highly structured information are combined by ultra-fast brain rhythms. And this, neurally speaking, is how and where consciousness arises.

Our awareness gives us incredible gifts of understanding, though there is a heavy price to pay for such a vast consciousness. The organ that has grown so large and complex in order to support the amazing innovation machine of human consciousness is intensely fragile. We are especially prone to serious brain injury, which can persistently rob us of awareness. Thankfully, though, many new techniques are arising to diagnose the levels of awareness that may still secretly reside in brain-damaged patients. Extensions of this research are beginning to offer us a chance to "hear" these patients, just by reading their brain signals, and for them to communicate with the outside world. Some emerging methods may even allow us to restore some degree of consciousness to patients in which it is clear that awareness is tragically absent as a result of injury.

Cases where severe brain injury leads to a persistent twilight of awareness are, thankfully, relatively rare. Unfortunately, though, the fragility of the human brain manifests very commonly, in more subtle forms. For optimum consciousness to occur, a complex interplay of various brain chemicals and activity between regions must be balanced just right. Some people have genes that make brain instabilities likely, and much of the population can be repeatedly battered by life's stressful events, which further strains their intricate neural machinery. The result can easily be mental illness, a pandemic that gets far less focus than it deserves.

But vital new clues in both understanding and treatment are arising, with almost all psychiatric conditions being repainted in terms of disorders of awareness. Various techniques that literally expand and reinvigorate consciousness are being successfully applied to almost all psychiatric patient groups. However, this is not just the story of what consciousness is, and when it breaks down, but how we can apply this knowledge to aid our daily lives. For instance, many of these awareness building approaches could just as easily be adopted by all of us, both to reduce the daily weight of stress we endure and to enable us to view the world more directly, with fresh eyes. And, in time, we can learn tenderly to nurture a consciousness that is quiet, open, and ready to discover many beautiful new patterns around us.